Vascular and venous valve implant prostheses

ABSTRACT

Exovascular and endovascular stent devices and associated support/restrictor assemblies for use in conjunction with prosthetic vascular grafts, including venous valve grafts made from preserved bioprosthetic venous valves. Also disclosed are methods for preparing vascular grafts such as venous valve grafts using the devices and assemblies of the present invention.

This application is a division of application Ser. No. 08/264,225 filedJun. 22, 1994 (now U.S. Pat. No. 5,609,626), which is a continuation ofapplication Ser. No. 07/871,414 filed Apr. 21, 1992 (abandoned), whichis a continuation-in-part of application Ser. No. 07/500,821 filed Mar.28, 1990 (abandoned), which is a continuation-in-part of applicationSer. No. 07/359,449 filed May 31, 1989 (abandoned).

FIELD OF THE INVENTION

The present invention relates generally to bioprosthetic vascularimplants and, more particularly, to stents and support/guide assemblieswhich are operative to (a) provide support for, (b) facilitate theimplantation of, and (c) minimize thromboembolic complications resultingfrom artificial or bioprosthetic vascular implants.

BACKGROUND OF THE INVENTION i. Prosthetic Vascular Grafts IncludingVenous Valvular Implants

Modern vascular surgical procedures often involve the grafting of atubular prosthetic implant of artificial or natural origin into anexisting blood vessel for the purpose of replacing or bypassing asegment of diseased or damaged blood vessel. Many such procedures areaccomplished by surgically removing the diseased or damaged segment ofblood vessel, and subsequently replacing the removed segment of vesselwith an appropriately sized tubular implant graft. The implant graft istypically held in place by anastomosing the ends of the implant graft tothe opposing ends of the resected blood vessel.

In individuals who suffer from chronic venous valvular insufficiency,vascular grafting procedure have utilized to transplant functioningvenous valves into the affected veins of the lower extremities. Thetransplantation of functioning venous valves in such individuals istherapeutically important as chronic incompetence or absence of venousvalves into the veins of the lower extremities is known to give rise tonumerous pathological consequences. For example, incompetence or absenceof venous valves at the saphenofemoral or saphenopopliteal junctions mayresult in noncosmetic varices of the primary and/or secondary veins ofthe lower leg and ankle. Additionally, deep venous hypertension of thelower limb may occur. Such venous hypertension may result in lymphedema,aberrant pigmentation of the skin and, in severe cases, the formation ofnecrotizing lesions known as "venous ulcers".

Surgical transplantation of one or more functioning venous valves into avalve-deficient vein is a viable means of restoring venous valvularfunction to the valve deficient vein. The routine use of venous valve"transplant" procedures has heretofore been largely limited to autograftprocedures. Such autograft procedures require the initial surgicalexcision of an autologous segment of viable vein (i.e. vein having afunctioning venous valve therein) from one site within the patient'sbody, followed by subsequent transplantation of the harvested autograftto other veins wherein the venous valvular insufficiency has occurred.Such autograft transplant procedures are problematic because of (a)difficulties encountered in locating suitable segments of vein havingviable venous valves therein and/or (b) the necessity of forming aseparate incision or second surgery to harvest the venous valveautograft and/or (c) size mismatching of the harvested venous valveautograft relative to the implant site as may result in subsequentthromboembolic complications and failure of the implanted valve.

In view of the limitations and shortcomings of autograft venous valvetransplantation procedures, it is desirable to develop artificial and/orpreserved venous valve implants from cadaverous human or animal sourcesfor subsequent transplantation into a human patient. The availability ofartificial or bioprosthetic venous valve implants would eliminate theneed for second-incision harvesting of homograft tissue and would enablethe surgeon to select from an available range of graft sizes to obtain agraft which is specifically size-matched to the diameter of the resectedblood vessel.

ii. Presently Known Methods of Preparing Bioprosthetic Grafts

Various chemical tanning or "fixing" procedures have been used topreserve and prevent the breakdown of collagenous tissue grafts. Such"fixing" procedures generally involve the bathing or immersion of thecollagenous graft tissue in a collagen cross-linking reagent. Examplesof methods for preparing chemically cross-linked collagen or graftmaterials are found in U.S. Pat. Nos. 2,900,644 (Rosenberg, et al.),3,927,422 (Sawyer), 3,966,401 (Hancock, et al.), 3,974,526 (Dardik, etal.), 4,239,492 (Holman, et al.) and 4,553,974 (Dewanjee).

Chemically fixed bioprosthetic heart valves and vascular grafts arecommercially available. Examples of prosthetic heart valves constructed,at least in part, from chemically fixed biological tissue are describedin U.S. Pat. Nos. 4,372,734 (Lane) and 4,443,895 (Lane). Examples ofbioprosthetic vascular grafts prepared from segments of mammalian bloodvessel are found in U.S. Pat. Nos. 4,671,797 (Varandecic) and 4,466,139(Ketharanathan, et al.).

iii. The Use of Stents to Support Bioprosthetic Tissue

Various rigid stent devices have heretofore been utilized to hold andsupport bioprosthetic implants, such as heart valves. Examples of stentdevices for bioprosthetic heart valves are described in U.S. Pat. Nos.4,816,029 (Penny, III, et al.) and 4,851,000 (Gupta).

iv. Thromboembolic Complications Known to Result from Turbulent BloodFlow Through Vascular Grafts

In the prior art, it has become recognized that abrupt variations in thelumenal diameter of a blood vessel, as may result from improper sizematching of a vascular implant graft, may result in thromboemboliccomplications due to the resultant non-laminar or turbulent flow broughtabout the abrupt variation in lumenal diameter.

In particular, accurate size matching of vein grafts is difficultbecause certain peripheral veins normally undergo large amounts ofdilation in performance of their normal physiological capacitancefunction. Thus, even if a vein graft is properly size matched at thetime of the surgical implantation, subsequent dilation of the endogenousvein at a location to the non-dilating vein graft may give rise toabrupt variations in lumenal diameter of the blood vessel.

Accordingly, there remains a need in the art for improved vascularimplant graft devices and techniques aimed at maximizing thebiocompatibility and ease of use of such vascular implant grafts, whileminimizing the potential for graft failure or other complications, suchas immunoreactions to the implant graft material and/or thromboemboliccomplications resulting from turbulent blood flow through the implantgraft.

SUMMARY OF THE INVENTION

The present invention overcomes some or all of the shortcomings of theprior art by providing an exovascular stent device and dilationrestrictor members, useable in connection with said exovascular stentdevice, for facilitating implantation and functioning of tubular implantgrafts such as vascular grafts and venous grafts having functioningvenous valves therein.

Additionally, there is provided an endovascular stent device whichoperates to hold and support a bioprosthetic venous valve forimplantation within the lumen of an existing blood vessel.

Further and in accordance with the invention there are provided systemsand methods of use, incorporating and utilizing the above-statedexovascular stent, dilation restrictor member(s) and endovascular stentdevices.

The exovascular stent device of the invention comprises an elongatetubular body having a hollow bore extending therethrough and flangesformed on either end thereof. A preserved segment of blood vessel ispositionable coaxially within the lumen of the exovascular stent deviceand the ends of such segment of blood vessel are outturned and attachedto the outboard surfaces of said end flanges, thereby forming a vascularimplant prosthesis.

The dilation restrictor member(s) of the invention comprise an apparatushaving an elongate tubular body with a hollow bore extendinglongitudinally therethrough and a flange formed about one end of saidtubular body. The tubular body is passable over the transected end of ablood vessel such that the transected end of said blood vessel emergesout of the flange end of said tubular body whereby it may be outturnedand affixed to the outboard surface of said flange. When so affixed tosaid blood vessel, the tubular body of the apparatus remains around theouter surface of the blood vessel, thereby functioning to restrictdilation of the blood vessel in the region of said tubular body.

A system or assembly of the present invention comprises the abovedescribed a) exovascular stent device and b) dilation restrictormember(s) in conjunction with one another. Optional spacer rings orwashers may be interposed therebetween to prevent tissue to tissuecontact between the excised end of the endogenous blood vessel and theadjacent end of the implant graft.

An endovascular stent device of the present invention comprises a rigidannular body having a hollow bore extending therethrough and first andsecond support struts extending longitudinally from one end thereof.Said support struts are configured and positioned to provide supportiveattachment for the lateral edges of a blood vessel graft wherein afunctioning venous valve is positioned. Accordingly, such endovascularstent device may be utilized as a rigid support device for the formationof a bioprosthetic venous valve implant which is insertable into thelumen of an existing vein. An annular ridge or other attachment means isformed on the outer surface of the endovascular stent to permit anexternally applied ligature or other attachment means to hold theendovascular stent (and the accompanying venous valve implant, inposition within the lumen of the blood vessel).

Further and more specific aspects of the invention will become apparentto those skilled in the art upon reading and understanding of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of an exovascular stentdevice of the present invention positioned next to a bioprosthetic veingraft segment which has a venous valve located therein.

FIG. 2 is a perspective view of a first embodiment of an exovascularstent device of the present invention.

FIG. 3 is a perspective view of the first embodiment of the exovascularstent device of the present invention having a bioprosthetic vein graftoperatively positioned therein.

FIG. 4 is a longitudinal sectional view through line 4--4 of FIG. 3.

FIG. 5 is an end elevational view of the exovascular stent device shownin FIG. 2.

FIG. 6 is a perspective view of a tapered ring-support member usable inconjunction with the exovascular stent device of the present invention.

FIG. 7 is a perspective view of a gasket member usable in conjunctionwith the exovascular stent device and tapered ring-support device of thepresent invention.

FIG. 8 is a perspective view of an alternative gasket member usable inconjunction with the exovascular stent device and tapered ring-supportmember of the present invention.

FIG. 9 is a perspective view of a vascular implant system of the presentinvention comprising (a) an exovascular stent device; (b) two (2)dilation restrictor members and (c) two (2) gaskets, said system beingshown in an in situ, operative position on a blood vessel.

FIG. 10 is a longitudinal sectional view through line 10--10 of FIG. 9.

FIG. 11 is a perspective view of a first alternative embodiment of adilation restrictor member usable in conjunction with the exovascularstent device of the present invention.

FIG. 12 is a perspective view of a second alternative embodiment of adilation restrictor member usable in conjunction with the exovascularstent device of the present invention.

FIG. 13 is a perspective view of a first alternative embodiment of anexovascular stent device of the present invention.

FIG. 14 is a perspective view of a second alternative embodiment of anexovascular stent device of the present invention.

FIG. 15 is a perspective view of a modified single-piece embodiment of avascular implant system of the present invention incorporating (a) anexovascular stent device component and (b) two (2) dilation restrictormember components.

FIG. 16 is a longitudinal sectional view through line 16--16 of FIG. 15.

FIG. 17 is an exploded perspective view of a modified version of thevascular implant system shown in FIG. 15, said modified version havingtapered interfacing surfaces on adjacent components to facilitatealignment of the components.

FIG. 18 is a longitudinal sectional view of the vascular implant systemshown in FIG. 17 when operatively positioned and mounted on an in situblood vessel.

FIGS. 19a-19d are step-by-step schematic diagrams illustrating a methodof implanting a prosthetic vascular graft utilizing a vascular implantsystem of the present invention.

FIG. 20a is a perspective view of a segment of bioprosthetic bloodvessel having a venous valve positioned therein.

FIG. 20b is a perspective view of an endovascular stent device of thepresent invention.

FIG. 20c is a perspective view of the endovascular stent device of FIG.20b positioned on and sutured to the bioprosthetic graft segment of FIG.20a.

FIG. 20d is a longitudinal section view through line 20d-20d of FIG.20b.

FIGS. 21a-21f is a step-by-step schematic diagram illustrating a methodof implanting a bioprosthetic venous valve within an in situ bloodvessel utilizing an endovascular stent device of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed descriptions and the accompanying drawings areprovided for the purpose of illustrating and describing certainpresently preferred embodiments of the invention. The following detaileddescriptions and drawings are not intended to limit the scope of theinvention in any way.

i. Exovascular Blood Vessel Stent Device

In accordance with the invention there is provided an exovascular bloodvessel stent device 10 which is useable to form a tubular implantprosthesis 13. The exovascular stent device 10 of the present inventionserves to hold and support a segment of tubular graft material such as asegment of blood vessel. In particular, the exovascular stent device 10of the present invention may be utilized in conjunction with a preservedsegment of vein having a venous valve position therein. In suchembodiment, the exovascular stent device 10 coupled with the preservedsection of venous valve having the venous valve located therein resultsin the formation of a venous valve implant prosthesis.

One embodiment of an exovascular stent device 10 of the presentinvention is shown in FIGS. 1-5. Referring to FIGS. 1-5, the stentdevice 10 comprises a cylindrical body having a hollow inner bore 22extending longitudinally therethrough and having a plurality of fluidpassage apertures 18, such as elongate slots (FIG. 2), formed therein.

A first end flange 14 is formed on one end of the cylindrical stent bodyand a second end flange 16 is formed on the opposite end of thecylindrical stent body. Suture holes or apertures 20 are formed in endflanges 14, 16 to facilitate suturing of a bioprosthetic blood vesselsegment 12 to the exovascular stent 10.

Initially, a segment of blood vessel 12, such as a segment of vein 12having a venous valve (V) formed therein, is excised and removed from acadaverous human or animal source. Excess tissue is removed from thesegment of blood vessel 12 and the prepared segment of blood vessel 12is thereafter immersed in or otherwise exposed to one or more chemicalfixative or preservative solutions for a period of time sufficient tochemically fix or tan the collagenous matrix of the blood vessel segment12, thereby forming a preserved bioprosthetic vascular graft.

Typically, the vein segment 10 is immersed in a chemical fixativesolution known to cross-link collagen molecules for purposes ofchemically "fixing" the collagenous network of the bioprosthetic veingraft. Examples of such chemical fixative solutions includeformaldehyde, glutaraldehyde, dialdehyde starch, hexamethylenediisocyanate and certain polyepoxy compounds including glycol diglycidylether, polyol polyglycidyl ether, and dicarboxylic acid diglycidylester.

After the chemical fixation process has been completed, the "fixed"segment of blood vessel is inserted into the hollow bore 22 of theexovascular stent device 10 such that some portion of the vein segment12 extends out of and protrudes beyond the opposite ends of the stentdevice 10. The protruding ends of the prosthetic vein segment 12 arethen rolled back or splayed laterally such that they abut against theouter faces of the lateral end flanges 14, 16. Portions of the veinsegment 12 which extend outboard of the outer edge of the flanges 14, 16are then trimmed or cut away such that the ends of the vein segment 12are substantially flush and even with the outer edges 24, 26 of theflanges 14, 16.

Sutures 28 are then passed through the ends of the vein segment 12 andthrough the suture apertures 20, thereby suturing the vein segment 12 tothe exovascular stent device 10 to form a substantially unitary implantprosthesis which comprises 1.) the vein segment 12 and the surroundingstent 10. It is preferable that the suture apertures 20 be slightlyelongate as shown, and sufficiently large to permit easy passage of astandard suture needle and suture material (e.g. 4-0 nylon)therethrough.

At the time of surgical implantation, the implant unit may be used inconjunction with one or two dilation restrictor members 30.Alternatively, the implant unit may be used with one or two anastomosisrims 31.

ii. Dilation Restrictor Members

In accordance with the invention, there is provided a dilationrestrictor member which functions to restrict the degree to which ablood vessel may dilate in a region immediately adjacent an existingsuture line. The dilation restrictor member 30 of the present inventionmay be utilized as an independent device or, alternatively, may beutilized in conjunction with the above-described exovascular stentdevice to form a complete vascular implant system.

The dilation restrictor member 30 comprises a generally cylindrical bodyhaving a flange member 32 formed on one end thereof. The cylindricalbody of the dilation restrictor member 30 may be tapered such that thediameter of such cylindrical body is smaller at the end adjacent theflange 32 than at the opposite end thereof. An example of such taperedconfiguration of the dilation restrictor member 30 is shown in FIG. 6.In such tapered embodiment, it is desirable generally cylindrical orfrusto-conical section of the restriction member 30 be configured suchthat its diameter gradually increases, thereby providing a gradual taperagainst which the outter surface of the blood vessel may abut when theblood vessel undergoes dilation or diametric enlargement.

The dilation restrictor member 30 serves two (2) functions. First, itoperates as an appliance to (a) facilitate suturing of the implantprosthesis 13 into the desired blood vessel. Second, the dilationrestrictor member operates to restrict dilation of the blood vessel 40at regions immediately adjacent the points of anastomosis to thevascular implant prosthesis 13. By restricting or limiting the dilationof the blood vessel 40 at regions immediately adjacent the implantprosthesis 13, the dilation restrictor members 30 function to prevent orminimize variations in internal blood vessel diameter between the innerdiameter of the implant prosthesis 13 and the inner diameter of theadjacent blood vessel 40. Such limitation helps to ensure laminar ornonturbulent flow of blood through the blood vessel 40 and implantprosthesis 13 without excessive turbulence.

In operation, the dilation restrictor member 30 is passed over the cutend of the blood vessel 40 such that the cut end of the blood vessel 40protrudes slightly beyond the opening of the inner bore 23 of thedilation restrictor member 30 at the flange 32 end thereof. The end ofthe blood vessel 40 is then splayed outwardly such that the outersurface of the blood vessel 40 abut against the outboard face of theflange 32. The end of the blood vessel 40 is then cut or trimmed suchthat on dilation of the blood vessel 40 immediately adjacent the pointsof anastomosis to the implant prosthesis terminates flush with orsubstantially even with the outer periphery 42 of the flange 32. Sutures44 are then passed through the end of the blood vessel 40 and the sutureapertures 34 to secure the end of the blood vessel 40 to the flange 32.

The exposed luminal surface of blood vessel 40 which faces away from theoutboard face of the flange 32 may then be placed in direct abutmentwith the exposed luminal surface of the prosthetic vein segment 12 whichfaces away from the outboard surface of adjacent lateral end flange 14or 16 of the supporting stent device 10. A series of interrupted ornoninterrupted sutures 50 may then be passed through the apertures 20,34 and the interpositioned tissue of the blood vessel 40 and prostheticvascular segment 12 to effect anastomosis of the prosthetic implant 13to the blood vessel 40.

iii. Optional Spacer Rings

An optional spacer ring or washer 50 may be interposed between thetissue of the blood vessel 40 and the tissue of the prosthetic vasculargraft 12 to prevent the living blood vessel tissue 40 from coming indirect contact with the preserved tissue of the prosthetic vasculargraft 12. The use of such spacer ring or washer 50 may minimize orprevent immunological reactions within the adjacent blood vessel 40 dueto contact with the preserved tissue of the prosthetic vascular graft12.

Such optional spacer ring or washer 50 may comprise a flat disc formedof biocompatible plastic such as Delrin™, acetyl resin (Dupont,Wilmington, Del. 19898), Teflon™, or other suitable materials. Thecentral aperture 52 of the spacer ring or washer 50 is preferably of thesame inner diameter D as that of the flange end opening of the dilationrestrictor member 30, and that of the end openings of the cylindricalbore 22 of the exovascular stent member 10. Such size matching of theinner diameters D of the adjacent portions of a.) the exovascular stentmember 10, b.) the spacer ring washer 50, and c.) the central bore 23 ofthe dilation restrictor member 30 will prevent or minimize thelikelihood of excessive turbulence or nonlaminar flow within the bloodvessel due to excessive variations of inner diameter of the bloodvessel, as may result if the implant components are not size matched.

iv. Vascular Implant System and Method of Use

The exovascular 10 the present invention may be coupled with one or moredilation restrictor members 30 to form a vascular implant system.Optionally, such vascular implant system may further incorporate spacerrings or washers 50. The individual exovascular stent 10, dilationrestrictor member(s) 30 and optional spacer ring(s) or washer(s) 50 maybe independently formed as separate components as shown in FIGS. 9, 10,17 and 18 or, alternatively, may be formed as a single-piece system asshown in FIGS. 15 and 16.

In embodiments of the invention wherein the exovascular stent 10dilation restrictor member (s) 30 and optional spacer ring(s) orwasher(s) 50 are favored as separate components the dilation restrictormembers 30 are positioned on the opposing cut ends of blood vessel 40with each cut end of blood vessel 40 being splayed outwardly and affixedto the outer face of the dilation restrictor member flange. Thebioprosthetic implant unit 13 incorporating the exovascular stent 10 ispositioned therebetween. Spacer rings or washers 50 may be interposedbetween the opposing surfaces of the blood vessel 40 and the prostheticvein segment 12 so as to prevent direct tissue-to-tissue contacttherebetween. Full thickness sutures are then utilized to anastomose thecomponents in end-to-end abutting relation, as shown in FIGS. 9 and 10.Notably, the sutures 54 pass through the flanges 14 or 16 and 32,through the adjacent out-turned tissue of the blood vessel and/orvascular implant 12 and through the optional washer or spacer 50. Suchsutures 54 thus remain outside of the blood-transporting vessel lumenand do not come in contact with the flow of blood which normally passesthrough the vessel following the implant surgery.

V. Anastomosis Rings

In applications where it is not desired to utilize a dilation restrictormember 30, a simple anastomosis ring 31, as shown in FIG. 12, may beemployed. Such anastomosis ring 31 comprises a rigid cylindrical rim 37having a perpendicular flange 33 formed on one end thereof. sutureapertures 35 are formed through the flange 33 as shown.

In operation, the rim 37 of the anastomosis ring 31 is passed over theouter surface of the cut end of blood vessel 40. The cut end of bloodvessel is then splayed outwardly or rolled back such that the outersurface of the blood vessel abuts against the outboard surface of flange33. The end of the blood vessel 40 is then cut or trimmed so as toterminate substantially flush with the outer periphery of flange 33.

Interrupted or uninterrupted sutures are passed through suture apertures35 and the adjacent tissue of the blood vessel 40 to affix theanastomosis ring 31 to the cut end of the blood vessel 40 in the desiredmanner.

Thereafter, the luminal surface of the blood vessel 40 which faces awayfrom the outboard surface of the flange 33 of anastomosis ring may beplaced in direct abutment with the surface of prosthetic vein segment 12which faces away from the outboard surface of the flange number 16 ofthe exovascular stent 10. Optionally, a spacer ring or washer 50 may beinterposed between the opposing surfaces of the blood vessel 40 and theprosthetic vein segment 12, as described above with respect to thedilation restrictor member embodiment of the invention.

Interrupted or uninterrupted sutures 50 are then passed through theadjacent tissues of the blood vessel 40 and prosthetic vein segment 12,through the adjacent suture apertures 20 and 35 of the stent device 10and anastomosis ring 31, respectively, and through any optionallyinterposed spacer ring or washer 50 so as to effect anastomotic couplingof the prosthetic implant 13 to the blood vessel 40.

In embodiments of the invention wherein the exovascular stent 10,dilation restrictor member(s) 30 and optional spacer ring(s) orwasher(s) 50 are formed as a single piece system (80 FIGS. 15 and 16).The exovascular stent component 10 will comprise the mid-portion 82 ofsuch single-piece system and will be formed of relatively rigid materialsuch as acetyl resin (Delrin™, Dupont, Wilmington, Del. 19898). Thelateral end portions 84 of such single-piece system 80 comprise thedilation restrictor member(s) 30 and are formed of elastomeric materialhaving greater elasticity than the relatively rigid mid-portion 82 ofthe single-piece system 80. Suture apertures 81 may be on the flangemembers 16b of the mid-portion 82 of the single-piece system 80 topermit passage of sutures 50A through the relatively rigid material ofthe mid-portion 82 of the system 80. On the otherhand, if theelastomeric material of the lateral end portions 84 of the single-piecesystem 80 is sufficiently flexible to be punctured by a suture needle,there need be no pre-cut suture apertures formed in the flange portion32b of such relatively flexible lateral end portions 84 of the system80.

Initially, a preserved segment of blood vessel 12b is positioned withinthe mid-region 82 of the single-piece system 80 such that the ends ofthe preserved segment of blood vessel 12b are splayed outwardly andpositioned adjacent the end flanges 14b, 16b. The ends of the bloodvessel segment 12b are affixed to the outboard surfaces of the endflanges 14b, 16b by way of an appropriate adhesive or by individualsutures 86. In embodiments where individual sutures 86 are employed, anadditional set of suture passage apertures 26b may be formed in the endflanges 18b, 14b to accommodate passage of such sutures 86.

With the prosthetic segment of blood vessel 12d affixed within themid-portion 82 of the single-pieced system 80, the entire system 80 maybe sterilized and stored in an appropriate storage solution such asglutaraldehyde or dilute ethanol.

At the time of implantation, the system 80 having the prosthetic segmentof blood vessel 24b mounted therein is rinsed and prepared forimplantation. A section of blood vessel 40b is excised and removed. Theremoved section of blood vessel corresponds to the length L of themid-region 82 of the single-piece system 80.

vi. Endovascular Venous Valve Stent Device

Further, and in accordance with the invention, there is provided anendovascular stent device 100 which is useable to form an endovascularvenous valve bioprosthesis 120. Such venous valve bioprosthesis isimplantable inside the lumen of a vein through an incision formed on thewall of the vein.

One embodiment of the endovascular venous valve stent device 100 of thepresent invention is shown in FIG. 20b. Such endovascular venous valvestent device 100 is formed of rigid, bio-compatible materials such asnylon, or Delrin™ (acetyl resin; Dupont, Wilmington, Del. 19898). Suchendovascular stent 100 comprises a generally cylindrical or tubular bodyhaving a hollow bore 108 extending longitudinally therethrough. Theinflow end of the rigid body 102 comprises a straight cut frustrumestablishing a generally flat, round opening into the hollow inner bore108 of the rigid body 102. The outflow end of the rigid body 102comprises two apical support struts 104, 106. Such apical support struts104, 106 are positioned on opposite sides of the rigid body 102 suchthat a fixed segment of blood vessel having a venous valve therein maybe positioned between and affixed to said support struts 104, 106, withthe lateral edges of the leaflets of the venous valve positioned thereinbeing directly adjacent to said lateral support struts 104, 106, suchthat the leaflets of the venous valve will traverse between thelaterally positioned support struts 104, 106 in the manner shown in FIG.20c.

Suture apertures 110 are formed at various locations on the rigid body102 to permit affixation of a segment of blood vessel 118 to theendovascular stent 100 by way of sutures.

At least one annular groove or ridge is formed around the rigid body 102to receive or facilitate seating of a ligature therein such that theimplant must be held in place by way of one or more blood vesselsurrounding ligatures 152, as shown in FIG. 21f.

vii, Preparation Of A Venous Valve Bioprosthesis For EndovascularImplantation

A preserved segment of vein 118 having a venous valve 119 positionedtherein may be mounted within the endovascular stent device 10 of thepresent invention to form an endovascular venous valve prosthesis 120,as shown in FIG. 20c.

Prior to preparation of the endovascular venous valve prosthesis 120, asegment of vein 118 having a venous valve 119 positioned therein isharvested from an autologous or homologous source and is subjected toany desired preparation, chemical fixing or other preservation stepssuch as those described in relation to the prosthetic implant 13described hereabove.

After the segment of vein 118 has been fully fixed and preserved, it iscoaxially inserted through the hollow bore 108 of the endovascular stent100, such that the opposite ends of the segment of vein 118 will extendout of and beyond the inflow and outflow ends of the endovascular stentdevice 100, as shown in FIG. 20c. The segment of vein 118 is rotated andpositioned such that the leaflets 122, 124 of venous valve 119 extendstransversely between the opposing support struts 104, 106 of theendovascular stent 110.

The portion of the vein segment 118 which extends out of and beyond theinflow end of the endovascular stent 100 is rolled back over the inflowend of the stent 100, trimmed and affixed to the body 102 of the stent100 by way of a series of interrupted or uninterrupted sutures 126.

Longitudinal incisions 128, 130 may be formed on opposite sides of theend portion of the vein segment 118 which extends out of and beyond theoutflow end of the stent 100. After incisions 128 and 130 have beenformed, that portion of the vein segment 118 may be rolled back over theouter surface of the body 102 of stent 100, trimmed, and affixed to thestent by rows of appropriately placed sutures 132, 134. Thus, the veinsegment 118 having venous valve 119 formed therein combines with theendovascular stent 100 to form an endovascular venous valve implantprosthesis 120.

A presently preferred method of surgically implanting the endovascularvenous valve prosthesis 120 is illustrated in FIGS. 21a-f.

Initially, the blood vessel 140 into which the endovascular venous valveprosthesis 120 is to be implanted is cross-clamped at first 144 andsecond 146 locations, on either side of the location at which theimplant is desired to reside. Thereafter, an incision 142 is formed inthe blood vessel 140, between the cross-clamp locations 144, 146. Theincision 142 is sufficiently large to permit the implant 120 to beinserted therethrough.

Double needle sutures 148, 150 are passed through the suture apertures110 located at or near the tips of the support struts 104, 106 of theimplant 120. Double needle sutures 148, 150 thus form convenient meansfor pulling or towing the implant 120 to a desired location within thelumen of the blood vessel 140, as illustrated in FIGS. 21c and 21d.Accordingly, the needles of sutures 148 and 150 are grasped by a needleholder instrument, inserted through incision 142 into the lumen of bloodvessel 140 and subsequently passed outwardly through the wall of theblood vessel 140 at opposite locations whereat it is desired to have theoutflow end of the implant 120 reside. Thereafter, the sutures 148 and150 may be pulled in the direction of arrows A while the implant 120 isgently guided through the incision 142, as shown in FIG. 21d. Thepulling of sutures 148, 150 in the direction of arrows A is continueduntil the implant 120 has been fully received within the lumen of theblood vessel 140 and advanced to its desired location of residence. Mildtugging pressure may be maintained on sutures 148, 150 to ensure thatthe implant 120 will remain in its desire residence location duringsubsequent closure of the incision 142 and until application of apermanent holding ligature 152.

The incision 142 may be closed by appropriate vascular sutures or anyother known means for closing such incision. After the incision 142 hasbeen closed, the holding ligature 152 is position around the outercircumference 140 and snuggly tied in place so as to be nested withinthe annular groove 112 of the stent 100. Such nesting of the ligature152 within the annular groove 112 of the stent 100 serves to firmly holdthe implant 120 at its desired location of residence.

After the holding ligature 152 has been applied, one or both of theneedles on two needle sutures 148 and 150 may be cut off and the sutures148 and 150 extracted and removed. Alternatively, the sutures 148 and150 may be tied on the exterior surface of the blood vessel 140 andremain in place to provide additional holding of the implant 120 at itsdesired location of residence.

Although the invention has been described herein with reference tospecific embodiments thereof, it will be appreciated that variousalterations, additions, or modifications may be made to the hereindescribed embodiments without departing from the intended spirit andscope of the invention. Accordingly, it is intended that all suchalterations, additions and modifications be included within the scope ofthe following claims or the equivalents thereof.

What is claimed is:
 1. A vascular implant system for facilitating thesurgical implantation of a tubular vascular graft between opposing cutends of a blood vessel from which a segment has been resected andremoved, said system comprising:a) an exovascular stent componentconfigured to receive and hold said tubular vascular graft therein, saidexovascular stent component comprising:a tubular stent body having afirst end, a second end, and a hollow bore extending longitudinallytherethrough; a first flange formed around the first end of said tubularbody; a second flange formed around the second end of said tubular body;said stent component being sized relative to said tubular vascular graftsuch that said tubular graft is coaxially positionable in the hollowbore of said stent with the ends of said graft being in contact withsaid first and second flanges; and b) first and second dilationrestrictor components respectively positionable on the cut ends of saidblood vessel for limiting the extent to which said blood vessel maydilate relative to the size of said tubular vascular graft, each of saiddilation restrictor components comprising:an elongate tubular bodyhaving a first end, a second end and a hollow bore extendinglongitudinally therethrough; an outwardly extending flange formed aboutthe second end of said tubular body; the tubular body of such dilationrestrictor component being sized and configured to pass, first endfirst, over the cut end of said blood vessel such that said cut end maybe attached to the flange of said dilation restrictor component with thetubular body of said restrictor component remaining disposed around saidblood vessel to prevent said blood vessel from dilating to a size largerthan the hollow bore of said surrounding tubular body.
 2. A vascularimplant system according to claim 1, wherein the first and secondflanges of the tubular stent body and the outwardly extending flanges ofthe first and second dilation restrictor components have sutureapertures for suturing the exovascular stent component to the first andsecond dilation restrictor components.
 3. A vascular implant systemaccording to claim 1, wherein the hollow bore of each respectivedilation restrictor component is tapered so as to have a smallercross-sectional dimension at the second end thereof than at the firstend thereof.
 4. A vascular implant system according to claim 3, whereinthe cross-sectional dimension of the first end of the hollow bore ofsaid tubular body is 4-22 mm, and the cross-sectional dimension of thesecond end of the hollow bore of said tubular body is 5-24 mm.
 5. Anendovascular venous valve prosthesis, comprising:an endovascular stentassembly including a stent having a generally cylindrical body with ahollow bore extending longitudinally therethrough and inflow and outflowends, and first and second support struts formed on opposite sides ofthe outflow end of said cylindrical body and extending generallylongitudinally therefrom; and a preserved segment of vein having anouter wall and a venous valve positioned therein, said valve having twoleaflets extending generally longitudinally within said segment of veinwith lateral edges adjacent the outer wall; wherein said segment of veinis coaxially disposed within the hollow bore of said stent and attachedthereto such that the leaflets of the venous valve extend transverselybetween the opposed support struts of said stent with said lateral edgespositioned adjacent said struts, the stent and segment of vein adaptedto be implanted as a unit in a patient.
 6. An endovascular venous valveprosthesis according to claim 5, wherein the stent comprises a pluralityof suture apertures for facilitating suturing of the vein segment to thestent.
 7. An endovascular venous valve prosthesis according to claim 5,wherein the stent comprises at least one annular groove formed aroundsaid cylindrical body such that a surrounding ligature may be receivedand nested within said groove.
 8. A vascular implant system forfacilitating the surgical implantation of a tubular vascular graftbetween opposing cut ends of a blood vessel from which a segment hasbeen resected and removed, said system comprising:a) a stent componenthaving a tubular stent body having a first end, a second end, and aconduit extending longitudinally therethrough, and being configured toreceive and hold said tubular vascular graft coaxially therein, saidstent component further comprising:a first flange formed proximal to thefirst end of said tubular body; and a second flange formed proximal tothe second end of said tubular body; b) first and second interconnectionmembers for attaching the stent component to the cut ends of the bloodvessel, each interconnection member configured to receive a respectivecut end of said blood vessel and having a flange which attaches to therespective cut end, the flange of the first interconnection memberconfigured to be coupled to the first flange of the tubular body, theflange of the second interconnection member configured to be coupled tothe second flange of the tubular body.
 9. A vascular implant systemaccording to claim 8, wherein the first and second flanges of thetubular stent body have a plurality of suture apertures formedrespectively therein for suturing the tubular stent body to the firstand second interconnection members.
 10. A vascular implant systemaccording to claim 8, wherein each interconnection member has a taperedconduit extending therethrough.
 11. A method of generating a venousvalve prosthesis that is adapted to restore venous valvular functionwithin a valve-deficient vein of a patient, the method comprising thesteps of:extracting a vein segment from a biological source other thanthe patient, the vein segment comprising a valve reservoir having anintact venous valve formed therein, the venous valve having at least oneleaflet; processing the vein segment to preserve the venous valve in acondition in which the venous valve is competent under venousconditions; and assembling the prosthesis, the step of assemblingcomprising positioning a support structure over an exterior surface ofat least a portion of the valve reservoir.
 12. The method according toclaim 11, wherein the step of processing comprises exposing the veinsegment to a chemical fixing agent.
 13. The method according to claim11, wherein the support structure has a conduit extending therethrough,and the step of positioning comprises advancing the vein segmentcoaxially within the conduit.
 14. The method according to claim 13,further comprising attaching the vein segment to the support structurewith the valve reservoir positioned within the conduit.
 15. The methodaccording to claim 11, further comprising the step of implanting thevenous valve prosthesis within a human in place of a valve-deficientvein segment.
 16. The method according to claim 14, wherein the supportstructure includes first and second outwardly-extending flanges atopposite respective ends of the conduit, and the step of attachingcomprises spreading the first and second ends of the vein segmentoutward and attaching the first and second ends, respectively, to thefirst and second flanges.
 17. The method according to claim 11, whereinthe step of extracting a vein segment comprises extracting the veinsegment from a cadaverous human.
 18. The method according to claim 11,wherein the step of extracting a vein segment comprises extracting thevein segment from an animal source.
 19. The method according to claim11, wherein the support structure comprises a tubular member having afirst end and a second end, and wherein the step of assembling theprosthesis comprises suturing a first end of the vein segment to thefirst end of the tubular member and suturing a second end of the veinsegment to the second end of the tubular member.
 20. A method ofgenerating a venous valve prosthesis, the method comprising the stepsof:extracting a vein segment from an animal, the vein segment comprisinga valve reservoir having an intact venous valve formed therein, thevenous valve having at least one leaflet; processing the vein segment topreserve the venous valve in an operable condition; positioning asupport structure over an exterior surface of at least a portion of thevalve reservoir, the support structure having a conduit extendingtherethrough, and including first and second outwardly-extending flangesat opposite respective ends of the conduit; and attaching the veinsegment to the support structure with the valve reservoir positionedwithin the conduit, the step of attaching comprising splaying the firstand second ends of the vein segment and suturing the first and secondends, respectively, to the first and second flanges.
 21. The methodaccording to claim 20, wherein the step of processing comprises exposingthe vein segment to a chemical fixing agent.
 22. The method according toclaim 20, further comprising the step of implanting the venous valveprosthesis within a human in place of a valve-deficient vein segment.23. The method according to claim 22, wherein the step of implantingcomprises attaching a first cut of an existing vein of the human to thefirst flange, and attaching a second cut end of the existing vein to thesecond flange.
 24. A venous valve prosthesis that is adapted to restorevenous valvular function within a valve-deficient vein, the prosthesiscomprising:a harvested vein segment, the vein segment comprising a valvereservoir having a least one intact venous valve formed therein, thevenous valve having at least one leaflet, the vein segment beingconditioned to preserve the competency of the venous valve; and asupport member positioned over an exterior surface of at least the valvereservoir, the support member providing support for the valve reservoirfollowing implantation of the prosthesis.
 25. The venous valveprosthesis according to claim 24, wherein the harvested vein segment ischemically fixed.
 26. The venous valve prosthesis according to claim 24,wherein the support member is configured to prevent the overexpansion ofthe valve reservoir without inhibiting a normal dilation of the valvereservoir.
 27. The venous valve prosthesis according to claim 24,wherein the support member comprises a tubular member having a conduit,and the harvested vein segment is disposed coaxially within the conduit.28. The venous valve prosthesis according to claim 27, wherein thetubular member has a plurality of openings which extend through atubular wall thereof, the openings configured to allow fluid to passinto and out of the conduit following implantation of the prosthesis.29. The venous valve prosthesis according to claim 27, wherein thesupport member further comprises first and second outwardly-extendingflanges at first and second ends of the tubular member, respectively,and wherein first and second ends of the harvested vein segment areattached to the first and second flanges, respectively.
 30. The venousvalve prosthesis according to claim 27, wherein a first end of the veinsegment is attached to a first end of the tubular member, and a secondend of the vein segment is attached to a second end of the tubularmember.
 31. A venous valve prosthesis for implantation within a human,the prosthesis comprising:a harvested vein segment, the vein segmentcomprising a valve reservoir having a least one intact venous valveformed therein, the venous valve having at least one leaflet, the veinsegment being conditioned to preserve the venous valve in an operablecondition; and a support member comprising a tubular member having aconduit, and having first and second outwardly-extending flanges atfirst and second ends of the tubular member, respectively; wherein theharvested vein segment is disposed coaxially within the conduit with thesupport member is positioned over an exterior surface of at least thevalve reservoir, and wherein first and second ends of the harvested veinsegment are attached to the first and second flanges, respectively. 32.The venous valve prosthesis according to claim 31, wherein first andsecond ends of the harvested vein segment are sutured to the first andsecond flanges, respectively.
 33. The venous valve prosthesis accordingto claim 31, wherein the harvested vein segment is chemically fixed. 34.The venous valve prosthesis according to claim 31, wherein the tubularmember has a plurality of openings which extend through a tubular wallthereof, the openings configured to allow fluid to pass into and out ofthe conduit following implantation of the prosthesis.